Vehicle windshields typically include first and second glass substrates that are laminated to one another via at least a polymer interlayer (e.g., PVB). A low emissivity (low-E) coating is often formed on an interior surface of one of the substrates so that the coating is provided between the substrates and adjacent the polymer interlayer in the final windshield product. A low-E coating typically includes at least one infrared (IR) reflecting layer such as Ag, NiCr, or Au, that is provided between at least a pair of dielectric layers. Example dielectric layers include silicon nitride, tin oxide, zinc oxide, etc. Example low-E coatings are disclosed in U.S. Pat. Nos. 3,682,528; 4,898,790; 4,965,121; 5,514,476; 5,563,734; 5,800,933; 5,837,108; 5,557,462; 5,935,702; and 6,014,872; and U.S. Ser. No. 09/794,224 (same as WO 02/04375), the disclosures of which are all hereby incorporated herein by reference. Other example low-E coatings are disclosed in WO 01/66483 and WO 01/66482. Such low-E coatings are provided so that the windshield can block (i.e., reflect and/or absorb) significant amounts of IR radiation thereby preventing the same from reaching the vehicle interior.
However, it is often preferred that some areas of the coated glass substrate not be provided with the low-E coating. For example, it may be desired that the coating (e.g., low-E coating) not be provided in toll area(s) of the windshield, rain sensor area(s) of the windshield, and/or adjacent edge(s) of the windshield. Regarding toll areas of the windshield (e.g., used for toll sensors and/or garage door openers), the IR reflecting layer(s) of the low-E coating may tend to interfere with electromagnetic wave transmissions (e.g., RF) associated therewith thereby rendering the coating undesirable in such areas. The same applies to rain sensor area(s). Low-E coatings are also sometimes not desired immediately adjacent edges of a windshield in order to avoid corrosion. Thus, it is known to remove the low-E coating from select area(s) (e.g., toll window area, rain sensor area, and/or edge area) of the coated substrate after the coating has been formed, but prior to lamination.
Low-E coatings are typically removed from such area(s) of a glass substrate by using a grinding wheel, sandblasting, or the like. Unfortunately, the use of a grinding wheel for removing low-E coating portions from a glass substrate can lead to scratching of the underlying substrate. This is undesirable; especially in viewing areas of a windshield. Cycle time may also be lost if many area(s) of the coating have to be deleted.
U.S. Pat. No. 5,713,986 discloses another technique for removing a low-E coating from select area(s) of a glass sheet. In the '986 patent, a resist is printed on a select area of a glass substrate prior to sputtering. After the resist has been formed and dried, a low-E coating is sputtered onto the substrate including in the select area over the resist. After formation of the coating, the resist along with the coating portion formed thereon is removed thereby deleting/removing the coating from the select area of the substrate. The result is a substrate that is coated with the low-E coating, but where the coating has been removed from the substrate in only the select area. In order to remove the resist (and the coating portion thereon), the '986 patent states that the coated substrate is soaked in hot water, and thereafter requires that hot water under high pressure at a temperature of at least 77 degrees C. (more preferably at least 85 degrees C.) is sprayed onto the substrate in order to remove the resist and the coating portion thereon.
Unfortunately, the technique of the '986 patent is undesirable because (a) it requires water at a very high temperature of at least 77 degrees C. to remove the resist, and/or (b) the materials used for the resist are collectively undesirable. For example, the high temperatures needed for removal are not desired, as they increase production costs and/or burdens.
In view of the above, it will be appreciated that there exists a need in the art for an improved technique for removing a coating portion from select area(s) of a coated substrate (e.g., in the manufacture of a vehicle windshield).